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Research Fellows Directory

Geoff Vallis

Professor Geoff Vallis

Research Fellow


University of Exeter

Research summary

My research is in climate and planetary atmospheres and it is motivated by two questions.

1. What processes determine the overall state of the climate of Earth and other planets?

2. How might the climate change in the future as a response to increased levels of greenhouse gases, and how might it have changed in the past?

Greenhouse gases are gases such as carbon dioxide that trap the radiation emitted from Earth's surface and so warm the surface. Although the warming effect is virtually certain, it is not known what other effects will arise, such as changes in regional climate or weather.

My research proceeds on two, frequently intersecting, tracks. On one track we use complicated computer models that try to simulate all the important processes that determine climate. These models utilize the world's largest computers to solve the known laws of physics and chemistry on a three-dimensional grid covering Earth's atmosphere, ocean and land. Yet the models have two shortcomings. First, it is impossible to include everything, so that we have at times to make empirical or even arbitrary choices as to how to deal with some small but important phenomenon, like a cloud. Second, the models are enormously complex and simply and trying understand the models (never mind the real climate system!) is very difficult. Because the system is so complex, small changes can have large and unforeseen effects

The other track to my research is to try to strip the system to its bare essentials, to construct models that display the essence of a phenomenon with no extraneous detail at all. These can help us understand the system better and, of practical benefit, improve the sophisticated models we use to predict weather and climate.

The benefit to society lies in being able to better predict the weather and climate as the planet warms, and to know the uncertainty of these predictions, and to put Earth's atmosphere and climate in the broader context of other planets in the Universe.

Interests and expertise (Subject groups)

Grants awarded

Geophysical Fluid Dynamics and Climate

Scheme: Wolfson Research Merit Awards

Dates: May 2014 - Apr 2019

Value: £50,000

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